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This study focuses on the Byzantine glass tesserae from Hierapolis (Phrygia, central Turkey). Fifty-seven samples of loose tesserae from two sites in the town (the theatre and the church of St. Philip) are analysed by particule-induced X-ray emission and particule-induced gamma ray emission and electron probe X-ray microanalysis to obtain the chemical composition and identify the colourants and opacifiers. The aims are to add new information to the scant knowledge of the Byzantine glassmaking technology, to constrain the chronology of the mosaics and to trace the supply routes of the tesserae. In the destruction layers of the theatre, tesserae produced following the Roman glassmaking technology (natron glass opacified by calcium and lead antimonate) were found. They were made using a Levantine 1 raw glass, generally attributed to the early Byzantine period (fifth to sixth c.). In the church, the samples attest a technological change from Roman tradition, and a complex pattern according to building history (two phases are attested, probably in the sixth and eighth to ninth c.), and a multiplicity of supply. Three glass types and some recipes not attested before in this chronological range for the production of tesserae are documented, such as the use of a local low-chlorine natron glass for the production of black and red tesserae, the blue colouring by a source of cobalt with zinc in a natron glass tessera and the opacification with tin oxide (both in a lead-free and in a high-lead natron glass), as well as with quartz. [ABSTRACT FROM AUTHOR]

This article presents the results of an interdisciplinary investigation of the mosaics in the main chapel of the Durres amphitheatre, the interpretation and chronological attribution of which have been the subject of debate. Art historical considerations about the mosaic's cultural and artistic affiliations are combined with in situ assessments of the mosaic techniques and physico-chemical analyses of 111 glass tesserae by means of scanning electron microscopy with an energy-dispersive detector (SEM-EDS) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS). Our results show that the raw glass used for the mosaic tesserae derives from two primary production centres but with evidence of substantial recycling: Foy-2, possibly of Egyptian origin, and Levantine I from the Syro-Palestinian coast. While lead stannate, copper and manganese are colorants found commonly in tesserae from different Mediterranean contexts, cobalt correlated with nickel and lead-tin associated with arsenic and antimony have been attested in mosaic tesserae here for the first time. The chronological range of the raw glasses and colorants provides strong evidence for a sixth- to eight-century CE date for the tesserae. The stylistic and iconographic parallels of contemporary mosaic decorations and the mosaic techniques reflected in the plaster layers, preparatory paint and particular setting of tesserae corroborate this timeframe. In terms of the material provenance and artistic features, the mosaics of the Durres amphitheatre clearly reflect the merging of eastern and western elements, typical of the early medieval Adriatic, while visual references to Byzantine imperial iconography may have served to reassert a link with Constantinople and the Byzantine court. Taken together, the material, technical and artistic data reveal the cultural and economic connectivity that shaped the art of mosaic making in the late antique and early medieval period. [ABSTRACT FROM AUTHOR]

Fifty-eight gold leaf tesserae from eight archaeological sites situated in the Byzantine Empire and two Early Islamic (one in medieval Palestine), covering the period that goes from the 4th c. to the 12th c., were analysed by EPMA, SEM-EDS and PIXE-PIGE to determine the composition of both the glass and the gold leaves. The good match until the 6th c. between circulating monetary alloys and the gold leaf compositions together with the type of glass used, provided criteria that can be used to date the tesserae fabrication. The data obtained allow newly produced tesserae to be distinguished from re-used ones. Because after the 7th c. the circulation of gold in the Byzantine Empire was less controlled, the same relationship is harder to establish. The results suggest the existence of workshops in the Eastern and Western part of the Mediterranean and a more advanced technology to manufacture a palette of glass colours for gold leaf tesserae in the Eastern region. [ABSTRACT FROM AUTHOR]

Abstract: An archaeometric study was carried out on 40 gold leaf tesserae from mosaics in Italy dated 1st to the 9th century AD. Glass layers and gold leaf were both analysed by X-ray microanalysis. The main aim was the identification of the composition of the glass and of the gold leaf, in order to assess the variations in composition and nature of the tesserae in the examined period. The analytical results show that the tesserae were obtained with natron type glass; three compositional groups were identified, each characterized by a specific colour. The coexistence of colourless (antimony-manganese as decolourizer) and naturally coloured (manganese as decolourizer) glass in each mosaic suggests the simultaneous use of the two materials, probably related to aesthetic choices. The analyses of the gold leaves indicate the use of pure gold or of gold-silver alloys. The good matches between the compositions of the gold leaves and the analyses of contemporary gold coins in the late antique and byzantine samples (3rd–9th c.) suggest that the leaves were made by beating circulating gold coins. This, in some cases, can help the dating of the tesserae and a more precise information on the type of glass used in this period. [Copyright &y& Elsevier]